On one hand, to extend coverage of a base station and improve a coverage effect of the base station, or due to other reasons, a small cell such as a relay node cell (relay cell), a pico base station cell (pico cell), a home NodeB cell (a femto cell or a Home eNodeB), or the like is introduced in a communications system. As shown in FIG. 1, on one hand, the small cell performs data transmission with a base station such as an access point (access point) by using a backhaul link (backhaul link), and on the other hand, performs data transmission with a wireless terminal (for example, a user terminal (User Equipment, UE)) by using an access link (access link). In this way, communication between the base station and the wireless terminal is implemented by using a relay node, and coverage of the base station is extended.
The base station and the small cell may be connected in a wireless or wired mode (for example, by using an optical fiber). FIG. 1 shows that the base station and the small cell are connected in the wireless mode.
On the other hand, it is theoretically feasible that a wireless communications device performs transmission and reception simultaneously on a same carrier. However, a signal transmitted on a transmit link by the wireless communications device is always leaked to a receive link of the wireless communications device, and causes interference to the receive link. Therefore, in an implementation, the wireless communications device is not allowed to perform transmission and reception simultaneously on the same carrier.
Herein, simultaneous transmission and reception on the same carrier are referred to as “full-duplex”. A potential full-duplex application includes: a small cell receives a signal from a base station, and simultaneously transmits a signal to a nearby wireless terminal by using a same physical layer resource, for example, a same carrier.
Currently, considering the foregoing problem of interference from the transmit link to the receive link, generally, full-duplex communication on the same subcarrier is generally not implemented in the wireless communications system.
For example, the 3rd Generation Partnership Project (the 3rd Generation Partner Project, 3GPP) release 10 (release 10) specifies that a wireless communications device cannot perform transmission and reception simultaneously on a same time-frequency resource, namely, a physical layer resource. In the release 10, information on a control channel is transmitted on a backhaul link between a base station and a relay node through a relay-physical downlink control channel (Relay-Physical Downlink Control Channel, R-PDCCH).
In a wireless communications system specified in the 3GPP release 10, because an R-PDCCH occupies a time-frequency resource of a physical downlink shared channel (Physical Downlink Shared Channel, PDSCH) of a base station, but a time-frequency resource of a conventional physical downlink control channel (Physical Downlink Control Channel, PDCCH) is vacant and unused, resource waste is caused.
In conclusion, in the current wireless communications system, to avoid interference caused by a backhaul link of a small cell such as a relay node, an additional physical control channel needs to be used on the backhaul link to transmit control information, and therefore, resource waste is caused.